// MIT License

// Copyright (c) 2019 Erin Catto

// Permission is hereby granted, free of charge, to any person obtaining a copy
// of this software and associated documentation files (the "Software"), to deal
// in the Software without restriction, including without limitation the rights
// to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
// copies of the Software, and to permit persons to whom the Software is
// furnished to do so, subject to the following conditions:

// The above copyright notice and this permission notice shall be included in all
// copies or substantial portions of the Software.

// THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
// IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
// FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
// AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
// LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
// OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
// SOFTWARE.

#ifndef B2_REVOLUTE_JOINT_H
#define B2_REVOLUTE_JOINT_H

#include "b2_api.h"
#include "b2_joint.h"

/// Revolute joint definition. This requires defining an anchor point where the
/// bodies are joined. The definition uses local anchor points so that the
/// initial configuration can violate the constraint slightly. You also need to
/// specify the initial relative angle for joint limits. This helps when saving
/// and loading a game.
/// The local anchor points are measured from the body's origin
/// rather than the center of mass because:
/// 1. you might not know where the center of mass will be.
/// 2. if you add/remove shapes from a body and recompute the mass,
///    the joints will be broken.
struct B2_API b2RevoluteJointDef : public b2JointDef
{
  b2RevoluteJointDef()
  {
    type = e_revoluteJoint;
    localAnchorA.Set(0.0f, 0.0f);
    localAnchorB.Set(0.0f, 0.0f);
    referenceAngle = 0.0f;
    lowerAngle = 0.0f;
    upperAngle = 0.0f;
    maxMotorTorque = 0.0f;
    motorSpeed = 0.0f;
    enableLimit = false;
    enableMotor = false;
  }

  /// Initialize the bodies, anchors, and reference angle using a world
  /// anchor point.
  void Initialize(b2Body* bodyA, b2Body* bodyB, const b2Vec2& anchor);

  /// The local anchor point relative to bodyA's origin.
  b2Vec2 localAnchorA;

  /// The local anchor point relative to bodyB's origin.
  b2Vec2 localAnchorB;

  /// The bodyB angle minus bodyA angle in the reference state (radians).
  float referenceAngle;

  /// A flag to enable joint limits.
  bool enableLimit;

  /// The lower angle for the joint limit (radians).
  float lowerAngle;

  /// The upper angle for the joint limit (radians).
  float upperAngle;

  /// A flag to enable the joint motor.
  bool enableMotor;

  /// The desired motor speed. Usually in radians per second.
  float motorSpeed;

  /// The maximum motor torque used to achieve the desired motor speed.
  /// Usually in N-m.
  float maxMotorTorque;
};

/// A revolute joint constrains two bodies to share a common point while they
/// are free to rotate about the point. The relative rotation about the shared
/// point is the joint angle. You can limit the relative rotation with
/// a joint limit that specifies a lower and upper angle. You can use a motor
/// to drive the relative rotation about the shared point. A maximum motor torque
/// is provided so that infinite forces are not generated.
class B2_API b2RevoluteJoint : public b2Joint
{
public:
  b2Vec2 GetAnchorA() const override;
  b2Vec2 GetAnchorB() const override;

  /// The local anchor point relative to bodyA's origin.
  const b2Vec2& GetLocalAnchorA() const { return m_localAnchorA; }

  /// The local anchor point relative to bodyB's origin.
  const b2Vec2& GetLocalAnchorB() const  { return m_localAnchorB; }

  /// Get the reference angle.
  float GetReferenceAngle() const { return m_referenceAngle; }

  /// Get the current joint angle in radians.
  float GetJointAngle() const;

  /// Get the current joint angle speed in radians per second.
  float GetJointSpeed() const;

  /// Is the joint limit enabled?
  bool IsLimitEnabled() const;

  /// Enable/disable the joint limit.
  void EnableLimit(bool flag);

  /// Get the lower joint limit in radians.
  float GetLowerLimit() const;

  /// Get the upper joint limit in radians.
  float GetUpperLimit() const;

  /// Set the joint limits in radians.
  void SetLimits(float lower, float upper);

  /// Is the joint motor enabled?
  bool IsMotorEnabled() const;

  /// Enable/disable the joint motor.
  void EnableMotor(bool flag);

  /// Set the motor speed in radians per second.
  void SetMotorSpeed(float speed);

  /// Get the motor speed in radians per second.
  float GetMotorSpeed() const;

  /// Set the maximum motor torque, usually in N-m.
  void SetMaxMotorTorque(float torque);
  float GetMaxMotorTorque() const { return m_maxMotorTorque; }

  /// Get the reaction force given the inverse time step.
  /// Unit is N.
  b2Vec2 GetReactionForce(float inv_dt) const override;

  /// Get the reaction torque due to the joint limit given the inverse time step.
  /// Unit is N*m.
  float GetReactionTorque(float inv_dt) const override;

  /// Get the current motor torque given the inverse time step.
  /// Unit is N*m.
  float GetMotorTorque(float inv_dt) const;

  /// Dump to b2Log.
  void Dump() override;

  ///
  void Draw(b2Draw* draw) const override;

protected:

  friend class b2Joint;
  friend class b2GearJoint;

  b2RevoluteJoint(const b2RevoluteJointDef* def);

  void InitVelocityConstraints(const b2SolverData& data) override;
  void SolveVelocityConstraints(const b2SolverData& data) override;
  bool SolvePositionConstraints(const b2SolverData& data) override;

  // Solver shared
  b2Vec2 m_localAnchorA;
  b2Vec2 m_localAnchorB;
  b2Vec2 m_impulse;
  float m_motorImpulse;
  float m_lowerImpulse;
  float m_upperImpulse;
  bool m_enableMotor;
  float m_maxMotorTorque;
  float m_motorSpeed;
  bool m_enableLimit;
  float m_referenceAngle;
  float m_lowerAngle;
  float m_upperAngle;

  // Solver temp
  int32 m_indexA;
  int32 m_indexB;
  b2Vec2 m_rA;
  b2Vec2 m_rB;
  b2Vec2 m_localCenterA;
  b2Vec2 m_localCenterB;
  float m_invMassA;
  float m_invMassB;
  float m_invIA;
  float m_invIB;
  b2Mat22 m_K;
  float m_angle;
  float m_axialMass;
};

inline float b2RevoluteJoint::GetMotorSpeed() const
{
  return m_motorSpeed;
}

#endif
